unable to mock patch in python unittest

I have developed the logic where I am initializing a few variables but with two versions.

Initially, my code looked something like this:

session = boto3.session.Session()
client = session.client(
    service_name='secretsmanager',
    region_name="eu-west-1"
)
class MyRepo(object):

So here, I was able to mock the client directly using a patch because it wasn't an instance variable.

After I implemented dependency injection:

class MyRepo(object):
    def __init__(self, region):
        session = boto3.session.Session()
        self.client = session.client(
            service_name='secretsmanager',
            region_name=region
        )

Now, I am trying to mock the instance variable which is accessed using the self keyword i.e client.

@patch('credentials_repo.my_repo.client')
class TestSecretManagerMethod(TestCase):

However, when I run the test case it throws an error attached below:

raise AttributeError(
AttributeError: <module 'credentials_repo.my_repo' from '/Users/bgh/IdeaProjects/witboost.mesh.provisioning.outputport.snowflake/provisioner/.tox/py38/lib/python3.8/site-packages/credentials_repo/retrieve_credentials.py'> does not have the attribute 'client'

How can I mock the client? Is there any better way to do it?

source https://stackoverflow.com/questions/74880937/unable-to-mock-patch-in-python-unittest